This invention relates to hydraulic cylinder assemblies and a method for manufacturing such assemblies.
A hydraulic assembly includes a piston slidably disposed in a cylinder with a piston rod connected to the piston and extending through a guide assembly supporting a seal at one end of the cylinder. Such guide assemblies prevent hydraulic fluid from leaking about the rod. Examples of such guide assemblies are shown in U.S. Pat Nos. 4,532,856 to Taylor; 4,987,826 to Deppert et al and 5,127,497 to Struckmeyer et al.
One of the problems associated with prior assemblies is that it is very difficult and expensive to attain very close tolerances with the piston rod. Large tolerances allow the extrusion of seals into the gap between the guide material and the rod. Accordingly, the closer the tolerances between the guide material and the rod, the more effective and longer life of the seal between the guide and the rod.
A method for manufacturing a guide for surrounding and sealing a rod in the end of a hydraulic cylinder including a piston slidably disposed in the cylinder and attached to the end of the rod. The method comprises the steps of: forming an annular guide from metal and having end faces interconnected by an outer mounting surface and an inner guide bore; forming a least one annular channel in the guide bore; placing the guide in a mold defining a cylindrical cavity extending about the guide bore and between the end faces of the guide; filling the cylindrical cavity with an organic polymeric bearing material; curing the bearing material: and removing the guide from the mold. The method is characterized by forming the channel with a mechanical interlock in the radially inward direction and curing the bearing material to radially contract and exert a radially inwardly directed force against the mechanical interlock and machining rod engaging surface into the interior of the bearing material.
The method, therefore, produces a guide for surrounding and sealing a rod in the end of a hydraulic cylinder including a piston slidably disposed in the cylinder and attached to the end of the rod wherein the guide comprises end faces interconnected by an outer mounting surface and an inner guide bore with at least one annular channel in the guide bore and an organic polymeric bearing material disposed in the guide bore. The guide is characterized by the bearing material and the channel including a mechanical interlock in the radial direction to exert a radial retaining force from the channel to the bearing material to establish a force fit in the radial direction between the channel and the bearing material.
Accordingly, the subject invention provides an improved guide with very close tolerances between the rod and the guide to increase seal effectiveness and life.